I experienced rough pressure using fingers on the vaginal area from above the underwear which was painful in the moment. no penetration occurred. after, i found a few drops of blood on the underwear. what could this be?clitoris?friction?hymen?

It is not feasible to provide a meaningful opinion without additional history, and physical examination. It does not appear to be a serious injury and should heal. If bleeding persists, it would be prudent to see a doctor. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines