something most people forget when doing excessive sit-ups is that abdominals are muscles and they need time to rest and recover just like any other muscle in your body.
Hello!
You have started exercising only since 2 days, give 48 hours rest to your abdominal musculature and you will be fine and after that exercise regularly in a graded and progressive way.
Take some NSAIDs.
Take care!
When you workout your muscles tear. This is normal for the beginning of exercise, just continue your workout after the first week or two your pain will go away.
And whether you continue your workout or not you will feel pain. But I recommend fighting through it and continue your workout for me, the pain goes away faster continuing the workout rather then giving up.