Hi Doctor, I Have A Slight Concern About A Red

Hi doctor, I have a slight concern about a red spot I just noticed on my penis today. My concern comes because I recently received a handjob from a CSW about 3 days ago. Apart from the handjob, there was no other contact with the CSW. Would like to know if this looks like any STD related issue? Also, I have a tube of gentrisone cream at home - would it be ok to apply onto the red spot?