The only way to identify a staph infection is to take a culture from the affected area and see if the bacteria grow out. Staph infection on the skin can present in many different ways, so you can t tell by just looking at it. You could get an abscess or a pimple-like lesion, or redness and tenderness of the skin, or a sore. Such lesions could be caused by other bacteria besides staph. If you suspect you might have a bacterial infection, be sure to keep it clean and you can try antibiotic ointment. If it is becoming an obvious abscess, or a cellulitis where the skin gets red, inflamed, and hot to touch, that could indicate an infection that needs treatment. In that case you should see your doctor for the appropriate treatment. Hope this helps.