I'm totally guessing here but you might want to do a little reading about iliopsoas tendinitis, iliopsoas bursitis and the psoas muscle. All of these can lead to hip pain, knee pain and pain in the groin.
While it's good to rule out all the "scary stuff", this sounds like a classic overuse injury caused by doing too much too soon. It might be helpful to get checked out by a physical therapist.
Good luck with your recovery. With a little rest and the right program, you'll hopefully be back on the bike very soon. Once you're healed, make sure you don't repeat the exact same pattern that caused the problem.