knee problem. help!

i haven't run for quite some time now. i remembered i last ran on chinese new year's eve, where I covered 6.4km in 34 minutes. I didn't really push myself and I felt I could cover at least 10km, but my left knee started feeling a bit weird after that run.

i just hope its nothing serious. it certainly felt okay when i went swimming yesterday, but when I tried running again today the slight throbbing and restrained feeling in my knee came back.

hopefully NS will be fine. i don't want to sit aside and be exempted from activities while the rest of my platoon execute them. that just sucks

any suggestions on how to cure it?