Left side of penis head has sharp pain when i touch it. no swelling, thin red rash under foreskin. slight pain while urinating. happened suddenly. thx?

Get checked: These symptoms aren't typical for any paticular cause. Injury or infection are most likely. Maybe nonspecific balanitis, which usually clears with hygiene (retract foreskin and wash 2-3 times daily), but herpes and other infections are possible. Or other STDs (e.g. gonorrhea, chlamydia) for the painful urination, if at risk for STD. If symptoms continue more than 1-2 days, see a doctor.