I think I made a big mistake.
It is one thing to post on a board saying you made a mistake. It is a better thing to try to fix the mistake. Contact admissions today. If they want the first semester grades make arrangements to have them sent/faxed over ASAP.
Also many colleges notify you if a piece of the application is missing so if you find the grades are required check with your guidance dept. to see if they already sent them out.