I am a fit cyclist but untrained for running, so I run 5k, 2 days in a row…

Since then, 3 weeks ago, I have serious muscle (quads) pain, and also strange skin sensitivity; I can hardly touch my leg. The pain goes all the way up to the left hip/lower back.

Did I do some damage to my leg muscles/ligaments/some kind of infection due to sudden stress? I did not see a doctor yet as I hope this will go away…

I know it is hard to get diagnostics over the internet…but that skin sensitivity symptom must be unique…Any ideas?

Thanks.