I'd suggest you should go for a specialist, although the pain might disappear someday (or probably has disappeared already).
I had about the same problem several years ago. At the first time the pain started a couple of hours after running 25KM and remained for about two weeks.
Whenever I tried to start exercising the pain came back and it took some days to recover. It went like this for more than two months when I eventually decided to see a knee specialist. He couldn't find anything, but he told me that next time it would be better to see him before trying to run again.
In case there's a serious problem that needs to be fixed you could cause further damage to your knee which possibly results in a running pause for the rest of your life!
Get well soon and see a doctor!
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