Welcome to the site - there's a lot of help to be found here, but be aware that you can find a lot of people who will greet any description of a knee problem from a runner with "you have to give up running!"
As a runner who has been through the mill of orthopedic surgery (starting with an op I never needed), I would say that you should definitely see a specialised knee OS, and preferably one who is a runner himself/herself. I have no idea what's causing your problem, but it doesn't sound like it's that serious. You may find that the old trick of Ice/elevation/compression/rest helps.
No meniscus problem can be conclusively proved without an MRI. If you find you do have a tear that requires surgery, it's always worth asking if that tear is in an area with enough blood supply for it to be repaired rather than removed. A repair takes longer to recover from, but leaves your knee in much better shape and at much less risk of arthritis long term.
One final piece of advice. If at all possible, avoid any surgery. And please get at least a second opinion before going under the knife. There are a lot of OS's out there who will get as many patients into the operating theatre as they can for $$ reasons. I discovered this to my cost.
Good luck with the problem, and with the race.