You should check with your Mohs surgeon as each surgeon has their own postoperative instructions. Generally for my patients, I recommend waiting to fly at least one week after the surgery. 99% of the time there is no need to see a patient but in the low chance of a postoperative side effect, it is preferable for the patient to come and see the surgeon who operated on them as they will be the most familiar with what is done.
I've had people fly in to see me for Mohs and fly out later that day. Also, I've done Mohs on several pilots and they fly the next day because it's their job! There isn't an issue with altitude or anything like that. But it would be more about your comfort level, any minor pain, the need for the any stitches to be removed a week or so later, and any needed follow-up with your physician if there are any concerns. As long as you're not flying away to somewhere where you can't find a doctor if you need one, or can't reach your physician by phone, I'd say you can fly whenever you want.