Mohs surgery 3 months ago for basal cell. It had completely healed, but now the area is red and a little swollen. (Photos)

While there are a number of reasons an area can become red and swollen three months after any surgery, including Mohs. The most likely explanation in your case is that absorbable sutures under the skin have simply not absorbed. While common absorbables such as Vycril are supposed to be absorbed in 28 days, this doesn't always happen. When they are not absorbed on schedule, your immune system will eventually recognize them as foreign and begin to break them down. Eventually, they usually work their way to the surface and exit or "spit" through to the surface, sometimes "marring" what had been a nice cosmetic repair. I've seen this happen with Vycril spitting as far out as 6 and 9 months. Because of this, I try to avoid using absorbables on the face whenever it's feasible. Warm moist compresses to the area in continuous fashion will increase blood flow to the area and hasten the response. Unfortunately, going in to remove the absorbables is not a reasonable option. Another possibility is that some tumor was left behind and is starting to grow. All that can be done in this case is to wait for it to surface and be identified. Since retained absorbable suture is the more likely explanation, I don't think it's in your best interest to go in surgically and verify what the problem is.