It all depends on a lot of things ... like where your foreskin has been ... how clean you keep yourself ... etc.
Not to scare you particularly, but that sounds like it could be a virus as in herpes; your brief description sounds very much like some I've seen. It could also be just abrasion from clothes. Or it could be bacterial from being hot, sweaty and maybe not getting as clean as it could in the shower. It could be another STD too. But almost all skin level infections are red, sore, and irritable, so ...
Bottom line, you do want to get it checked out; by a doctor, soon. Your doctor, the county health clinic, a walk-in clinic, wherever. Just don't delay having an expert view it.
We hope you find this general health information helpful. Please note however, that this Q&A is meant to support not replace the professional medical advice you receive from your doctor. No information in the Answers above is intended to diagnose or treat any condition. The views expressed in the Answers above belong to the individuals who posted them and do not necessarily reflect the views of Remedy Health Media. Remedy Health Media does not review or edit content posted by our community members, but reserves the right to remove any material it deems inappropriate.