I would do it now, then again in the middle of summer, and again in the winter to keep it at 7ft. Or if you don't have very much branching, cut it back to 5 or 6 ft now and let it grow out to 7ft over the summer then prune it back in the winter.

Don't prune them when they are dormant if you live in an area where cherries are prone to canker. Now and again later should be fine.

Ok, great. Thanks for the advice!