My question involves criminal law for the state of: TX

I was parked in my drive way with my car off talking to my gf on the phone when all of a sudden a cop turns the corner and sees my cellphone light before parking directly behind me. Before he steps out, I step out of my vehicle asking the officer what was wrong. He said that there have been a lot of car break ins recently and asked if I owned the car. I stated yes and then he proceeded to ask for my ID. My mistake was opening the car door and retrieving my ID because as soon as I opened the door he could smell marijuana. Once he smelled it he asked if I smoke which I said no and then asked if I smoked weed which I said no. He then used his flashlight to look into my car and saw 2 grams of bud. He asked if it was mine and I stated no that it was my friends. He then quickly hand cuffed me and searched me before throwing me into the back of his SUV.

I've already spoke to a couple of lawyers in the San Antonio area and they said that I have a good chance of fighting this and getting it expunged because my 4th amendment right was violated. However, before I proceed with anything I would like some advice from peers. BTW this is my first offense and I'm a medical student who's one year away from graduating. My biggest fear is that this class B misdemeanor will ruin my future....(not sure if this holds any weight, but my gf was on the phone the whole time). Any advice is greatly appreciated.