Outer/back portion of my left knee.
Looking into doctors right now, probably going to call around tomorrow for an appointment. (sick)
Don't go to a general practitioner for this one. I did, and it cost me big time. Tore my ACL and my doctor diagnosed it as a sprained knee. Few weeks later I went back to basketball and I tore my meniscus as a result. Go see an orthopedic doctor/surgeon. Back right of the knee pain might be a sprain or partial tear in the LCL if you're talking about your right knee. Left knee that would be the MCL. You could easily aggravate either one playing golf with the twisting motions of a swing.
Hope it turns out to be just a sprain and nothing more serious. Good luck.
Oops, my apologies. I pretty much never check the email that my paypal is linked to. If you need anything from me in the future just shoot me a PM for quicker response. For some reason I was thinking I did the 3 month thing and had awhile before it was due again, but I'll go ahead and send you another paypal even though I am still not actually selling anything yet.