Sounds like iliotibial band syndrome (ITB) to me. Usual advice is to lower the saddle and spend a lot of time stretching. Some people have to take considerable time completely off the bike. For things like this, I usually combine ibuprofen with stretching and time off. I take 600mg ibuprofen twice a day for about a week, whether it hurts or not, also stretching twice a day. Then give the bike a try without Vit I, but ride easy.

And give Google a try.