Thanks for your query.Based on the facts that you have posted it appears that your boyfriend has sustained injury
to his glans
during sex.Mostly he has a partial tear of Tunica Albuginea
a facial sheath that envelopes Corpora Cavernosa of the Penis.
This will take 2 weeks to heal completely .Take some anti inflammatory drug like Diclofenac
twice daily .Get prescription of the medicine from your family Physician.and avoid sexual activities till it gets cured .