The AC joint has some ligamentous structures for stability. If you disrupted those it will take a "while" to heal. Generally I am talking 8-10 weeks for a minor sprain. Shear force injuries can completely disrupt these and treatment options are varied. Some recommend surgery in atheletes, I would try conservative management. To determine if there is a seperation x-rays should be done of both shoulders while holding weights. An excessive enlargement in joint space on the affected arm suggests a seperation. See an orthopaedic doctor, preferably with a sports medicine practice.
On the other hand, you are 30 and some prior trauma or cummulative trauma could have affected the joint and created some wear. This can affect both the soft tissues and the cartilage. In that case, this grinding or popping noise is know as crepitance. If there is NO bump at the jointline or capsule then conservative management, PT, ice and NSAID's are appropriate. Unfortunately these do take a while to heal. (I'm deliberately vague)
I generally like a PT or AT involved and have them watch you do the routine. If the joint subluxes, STOP. See the ortho. Unstable joints accelerate cartilage wear and create new oppourtunities for orthopeadic surgeons. This is a 54 year old talking..lol
Nothing I offer is construed as medical treatment, just a guy talking to a guy ..... Medic