I wrote back (check PMs). This is actually not uncommon, I myself have experienced it; for some men, very aggressive and prolonged sex (or masturbation), or even penis pumping, can exhibit this swelling, which typically subsides in a few days. It's been reported numerous times throughout the years, and hasn't seemed alarming since it seems to respond to an aggressive physical stimuli (perhaps irritation or inflammation) and returns to normal relatively quickly.
What you should look out for is if it becomes painful, red, warm, and/or if the swelling worsens or persists for more than a few days. But this is not something that is observed with what I THINK you are likely experiencing -- but I don't know for sure, which is why I'm suggesting you monitor it for now.
If it is what I think it is, no it isn't anything alarming based on my experience and the experiences of others. I'm 15 years post-op with no complication, and that swelling can almost predictably be triggered should I choose to (but I don't advise men to intentionally do this, no need to flare up inflammation than is already present; if it happens it happens but most guys aren't typically applying aggressive external stressors regularly, so I think you'll be fine.