I'm not a physiotherapist so please consult someone before trying anything!

I have an irritation with my AC joint as well. And I'll be honest, playing a sport like tennis will only make it worse because your inflammation hasn't healed and you might have irritated it further. My best advice would be do perform very light stretches and exercises for your shoulder. Some pendulums, abduction/adduction, lateral abduction/adduction etc., is what I've been recommended. Progressively challenge yourself. Only 2 weeks of physio isn't going to help (unfortunately)! You could also ask them to remove scar tissue in the area which for me resulted in a lot of soreness in my shoulder and down my arm but allowed me to move a bit more.

Acupuncture, I've seen doesn't work for everyone the same way. I've seen some people who respond very well and others who do not.

I don't know your age, but nevertheless it might be wise to make sure you don't have osteoarthritis in the joint!

Anyone who is more experienced, please feel free to correct me if I'm wrong! =)