I wouldn't worry too much, they were expecting them (albeit this was a biggie). The L2 point it's at means there shouldn't be too much that collects around there, gravity wise, but it will happen again.
Hopefully it was just a fluke, but if not, this telescope will not survive it's intended lifespan.
As such, NASA has already started a project to optimize the orientation of the craft to minimize strikes.
So the overall number of impacts is consistent with the modeled rate, but the size of the C3 event was outside the modeled rate.