Short answer. Yes, it can still be a crime. Article 266 covers three situations: injuries needing one to nine days of medical attention or rest, injuries needing neither, and ill-treatment by deed causing no injury at all. Each carries its own lighter penalty.
What the law says
when the offender has inflicted physical injuries which shall incapacitate the offended party for labor from one (1) days to nine (9) days, or shall require medical attendance during the same period
Revised Penal Code, Article 266 — Slight Physical Injuries. Read the full provision →
What the law says
when the offender shall ill-treat another by deed without causing any injury
Revised Penal Code, Article 266 — Slight Physical Injuries. Read the full provision →
The nine-day line
What separates slight physical injuries from the heavier grades is time, not how painful it felt. The first paragraph applies when the offender has inflicted physical injuries which shall incapacitate the offended party for labor from one (1) days to nine (9) days, or shall require medical attendance during the same period. Nine days or fewer, and the offence is slight. Ten days or more moves the case into less serious physical injuries, and longer or permanently disabling harm moves it further still. This is why the medical certificate matters so much: the doctor's estimate of healing time or required medical attendance is usually what decides which article the prosecutor charges.
Injuries that need no doctor at all
The second paragraph catches harm that does not prevent the offended party from engaging in his habitual work nor require medical assistance — the bruise, the scratch, the swelling that heals on its own. Many people assume that if they did not go to hospital there is no case. That is wrong; this paragraph exists precisely for that situation, and it carries arresto menor or a fine, together with censure. It is still worth being examined and photographed on the same day, because the alternative is a complaint resting entirely on your word against the other person's, with no contemporaneous record of what your face or arm looked like.
Ill-treatment where nothing was injured
The third paragraph goes further and reaches conduct when the offender shall ill-treat another by deed without causing any injury. A shove, a slap that leaves no mark, hair pulled, a person manhandled — no wound, no medical certificate, and still an offence. The requirement is a physical act directed at the person; insults and threats alone belong to other provisions. This is the answer to the question people most often ask after an altercation: the absence of a visible wound does not end the matter. What it does change is the penalty, which here is the lightest of the three at arresto menor in its minimum period or a fine.
Amounts, limits, and what to do next
The fines in this article — not exceeding ₱40,000 for the second paragraph and not exceeding ₱5,000 for the third — are current because Republic Act No. 10951 (2017) revised the fines and property values throughout the Revised Penal Code. Older printings still carry the 1930 figures, which are far smaller, so check which version any source you rely on is giving you. Note the limits of this article too: it does not cover injuries inflicted on a spouse, partner or child in a domestic context, where a separate special law may apply and is usually the stronger route; it does not deal with the civil claim for your medical costs and lost income, which is pursued alongside; and as a light offence it prescribes quickly. Get examined the same day, photograph the injury, note down witnesses, and see a lawyer without delay.