Does a cop have a right to har you when you've done nothing wrong?

i was at a gas station and a cop walked ped me and said he smelled weed and keeped haring me about if i smoke weed or if i ever smoked and respectfully i answered him and said no after i paid for my gas i went outside and started pumping it and he came outside and started to har me again saying he smelled it around my car and searched around the pump but couldn't find anything he let me go then i picked up my friend and went to the mall as soon as i stepped out of my car 3 cops rush me and tell me to put my hands on the car then searched me put me in handcuffs and asked me if i was smoking weed and they searched my car without asking and couldn't find anything then let me go now all of that being said do they have the right to do that