I had an arthroscopic meniscus tear cleaned up/removed September of last year. Prior to the surgery, I had spent months trying to run on it until finally throwing in the towel and recognizing that it wasn't going to heal on its own.
The morning after the surgery, I was elated. The doctor told me I had no restrictions, and the pain was pretty much gone. I ran 7 miles the day after that, and then another 7 miles the next day. It hurt pretty bad, so I ended up taking a couple more weeks off and slowly ramping up. Apparently, it's pretty normal to need some time to recover.
I gotta say, it's been 10 months and I've been getting in 30 to 50 miles per week, but that knee is still not 100%. It doesn't "hurt" outright, but it feels "weird". I don't fully trust it, but at the same time, my lack of fitness is slowing me down more than it is. I went to base level fitness prior to the surgery and gained 30 pounds, so that may be part of my struggle. Things are definitely getting better, but it's taking more time than I would like.
At any rate, 12 weeks is not a long time to heal from something relatively traumatic, particularly if you are older. I'm 48, which is not crazy old, but may account for some of the time it's taking me to get back to normal. I recall when I broke my ankle at 27, it took more than a year to feel kind of normal and never fully recovered (if you can truly call it recovered) until I had the hardware removed many years later.
Hang in there and give it some time. I don't think there's any reason to panic at this point...unless you think your swelling is due to a festering infection. If that is the case, get a doctor who will treat it!