I demo'd my main bathroom, but won't have the contractor in for another 2-3 weeks to finish it up.

My issue is the spout is dripping water, about 20oz in 8hrs. It was leaking before, but now that there is no tub to catch it, it's an issue.

How do I fix this valve body? It's nothing I have seen in HOW TO videos online. Do I need to have my plumber fix this or is something I can easilly do?