Hi Lavina,
Most likely cause of your pain is hamstring tendonitis - at the point at which the three muscles of the hamstring join the bone (via a tendon) at the lowest part of your butt - the ischial tuberosity - a tear or pull in this area can cause the pain you mention and is made worse through sitting for long periods - it can also cause butt pain as your glutes try to take over some of the work while your hamstrings are effectively weakened, and it can irritate the sciatic nerve, although the latter is less likely.
This tendon, depending on how badly you have strained it could require up to 6 weeks rest from running - so 10 days is not a lot of time if the tear is bad.
However, you may be able to heal it more quickly by adding some of the following to your rest regime
- ice the area regularly
- do regular hamstring stretches (when muscles warm) but don't overdo them (look up the windmill stretch) and also do light hamstring strengthening work - curls for example - but with very light weights
- applying cross-friction massage might be helpful (but see caveat below) near the top of the hamstrings where they meet the bone of the butt - you will have to feel around up there for tender areas and use you fingers to gently work the area across it's length (not down it) -
- continue with any cross-training that doesn't cause tightness or pain in your hams
- possibly use ibuprofen - but sparingly - regular icing is better
If this regime doesn't show signs of improvement within two weeks, then I suggest you go see a physio for a more thorough assessment - you could have bursitis - that's inflammation of the bursa that sits between the tendon and the bone that normally reduces friction - symptoms can be very similar to tendinitis - same basic treatment would apply except for friction massage which could make it worse.
Regards, Groz