You're about my age right now. I tore the meniscus in my right knee. It really wasn't too bad, but would kind of swell up after longish days on it - long approaches, hiking, etc. I went like that for a couple years - I assume I messed up my knee crashing dirtbikes in my early 20s, but I'm not sure. About 5 years ago, I finally got it checked out, as I was sick of knowing something could be a liability at one point.
Got the whole X-ray/MRI gig. Partial tear - you could see it in the MRI. Doc said pretty common injury, blah, blah, blah. Got the surgery - just a couple small punctures where the tools are shoved in. Made me a nice DVD of the operation. Went smooth at first, but got a blood clot in my knee after 3 days - not the kind that could break and stroke you though. It made my knee swell up big time for a few weeks. Anyway, that is not too common. Some physical therapy helps get full confidence again, and a I was back 90% in probably 4 months. 100% shortly after. In reality I would say someone our age - 3 months or less would be common to get 100% physical and "mental" recovery.
I said I would never do that shit (surgery) again after that. Now, my knee is great. If you don't want to drop the cash, or have shitty "insurance", I'd say take it easy for a bit. Train upper body only for a few weeks, and give it time to heal - only if nothing devastating happened. Slowly work back into it, maybe some stationary biking, or chill biking is in order - it will help keep loose and range of motion.
Only you know if it's really fucked up. After a few weeks, if you don't think you can run, and then cut left or right real hard, get it looked at.