Infection

Hmmn well ah... the cut stays red and stays painful. If it's quite infected, pus starts forming. I would think you'd know after a day or two because instead of healing the cut will still be inflamed and more painful than initially.

Of course, the progression would depend on the bacteria infecting the cut and how strong your immune system is... some rare bacteria are quite virulent and dangerous but they are generally very, very rare (I'm thinking about flesh-eating disease here).

 

As joeyconnick has said above and sometimes the redness spreads out around the wound and depending on where it is too, you could get red lines running up towards the center of the body. Pain and swelling is hallmark though.

Treating it, Cleaning with antibacterial soap and water, making sure you have lots of suds with washing. Wash for at least 15-30 seconds and rinse. Apply an antibacterial ointment - neosporin, bactatracin, triple antibiotic ointment. Bandage. Change the bandage and clean it again at least once a day up to three times a day depending on how bad.

If it doesn't seem to get better in a day or so, see a doc. If there is red streaking seen, see a doc, as the infection is spreading via the lymph system.