Dazed and confused.what should i do about the way he touched me?

me and a group of people went to sixflags..two couples and myself and a friend.we had a good time..but at one point during the trip one of the guys with a girlfriend,the couple I work with(we all joke ect and are pretty close),had his arms outstretched in the back seat and started to caress my shoulder,started off really light,and then i turned and look at him(gave him that,yes its my shoulder your hand is on look)and he smiled and his hand went slighty further down...to the botton bikinni trap on my top.his gf was in the front seat.what should i have done.it seems like he and his gf are still affectionant so i got confused..is he trying to cheat with me or is he just being nice...i dnt know