Knee Pain

On Tuesday, the day after my long run, my knee began hurting/alot!
Not the kind of soreness I occasionally have after running. That seems to be my weight causing that. It goes away quickly. My conditioning has made that better.
In my right knee on the left side, which has me limping a litlle bit. I am currently taking naproxene and ibuprofen for the pain. It has me worried some..
Could it be overwork? Too much too fast? Probably..
By Wednesday it was feeling better, so I decide to run that night. No pain while running, but pain afterwards. Limped some on Thursday, felt better by night. No pain today(Friday)..
I desperately want to run after work, because I NEED TO! (Okay, I want to)... I am fighting my stubborness and will! Yes, I have read the articles about resting to avoid injury. Is this a true injury or is it growing pains. I've grown up with the philosophy of no pain,no gain.
I guess I'll decide tonight..hmmmmm