Thanks for your query.Based on the facts that you have posted it appears that you get bumps on foreskin every time after you have sex.
This is most likely to be to incomplete retraction of the foreskin during intercourse.(Partial Phimosis
Please consult qualified Urologist
to confirm whether you have Partial Phimosis.If confirmed you may need to undergo circumcised under local anaesthesia.
Please ake broad spectrum antibiotics along with anti inflammatory medication like Diclofenac
twice daily .
Get the prescription of medicines from your family Physician.
Ensure to clean your genitals with warm water twice daily.