I did the same thing on my very first road bike ride. i wasn't even 1 mile from home. I'd been practicing clipping in and out on a trainer and it all seemed so easy....I took my brand new bike on the road..took a few peddle strokes and then tried to stop and unclip. I beat myself up with the bike seat!! I also tore the seat on the ground and ripped up my bar tape. I didn't get rash, just big black bruises from the bike seat all over my rear end!!

Hope you heal quickly!