...i just half slept with my best friend ;(

the guy that i like he is 21 and he expected me to wait until i was older so that we could go out.... but i got sick of waiting cause i have been waiting for three months and i didnt feel that it was worth it...so last night me and my best friend were drinking...and we then went swimming...he came onto me ad bang boom the night went up in flames...we didnt have sex but we did everything else...in the middle of it the other guy i like called me and wanted to talk and i told him what i was doing and that i was sorry...so he hung up...i feel now that i have lost a good friend and may just mess things up...what do i do?