It sounds to me like you have irritated your IT band. (Iliotibial band.) I know because it's something that often happens to me!!!
Check this out
en.wikipedia.org/wiki/Iliotibial_band_syndrome.
Here are some common stretches that often help.
running.competitor.com/2015/03/injury-prevention/10-exercises-to-treat-it-band-syndrome_125083I would start with ice, in 20 minute increments. Maybe some very gentle versions of the stretches above. Of course, we are not Drs and before you do too much it would be good to get an official diagnosis and treatment plan.
Good luck!