Post 2 is all good information. Meanwhile, check your bike fit - here's my primer: How can I fitting my bike

Do these stretches every morning: IT Band pain (during ride)

While waiting for that to do some good, you can try taking 600 mg ibuprofen every 6 hours for a few days. If that fixes it, it was probably a swollen tendon sheath or bursa. If that doesn't fix it, and the above isn't working either, it's doctor time.

It's not overtraining in any case, but rather a minor injury caused by doing too much, too soon, without doing some attendant stretching and strength training.