I kind of had this a few weeks ago, but I'm not sure if mine was directly on the metatarsal or not. I could still run on it but I felt like it was affecting my right foot landing just a little bit, which would have been a risk for another injury. Since it was early in a base stage and I had no races coming up I took 6 days off from running, biked a couple days, ran in the pool once, and I was completely fine when I came back.
I also did foot drills, such as the towel drill, where you use your toes to drag a towel towards you with your heel on the ground. Also stretch you toes downwards to create an arch in your foot and hold for thirty seconds or so. Do the same stretch except opposite and much lighter, unless it hurts your metatarsal too much, then skip it.
Again, maybe my injury was different and I may not have needed 6 days off, but I wanted to make sure it went away, but it's worth a shot.