Swelling after masturbation (4 weeks post-op)

[Prospect17]

Hey guys, I went to see my surgeon yesterday and he said that my circumcision wound had fully healed and I was clear to go back to sport and sexual activity (easing into it). Today I masturbated pretty gently and ejaculated... about 30 minutes afterwards my penis was VERY swollen. I saw my normal doctor and he said the swelling will go down by itself but he’s not sure why it happened. Anyone know what could be the issue here that’s caused swelling after masturbation?

Thanks in advance!

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Blood supply