Lukewarm hot water in house after valve change in shower under construction

Sorry if this is a repost, it looks like the first post did not take...

We installed a rough-in valve in our master bathroom, we have only put the test cover on to the valve as the construction is still ongoing. Since the installation, the hot water in the other bathroom only gets up to lukewarm, not hot. Nothing else has changed. I think air got in the lines because I had a couple of faucets open when I was replacing my valve, I don't know if that is a big deal.

Whoever installed the rough in body did NOT install the bypass plug to prevent that from happening. If the plug has been lost or dislodged, you can install the valve cartridge to correct the problem.