New-onset Knee pain

[maphili]

I just started running again after close to a year hiatus. After my first run I now have a pain in my left knee when I walk up or down stairs. I had chondromalacia in my right knee before after 3 months of heavy traing a few years back. This doesn't feel like that at all. I did not injure or twist my knee and I have no restricted movement or clicking sensation. The pain feels inside the joint and more medial. Running or walking does not hurt. It is very annoying for someone who has never had a real injury before.

Thanks for any insight...