Ugh, this would be me. In one sense, of course it would take time (and broken pens) to try to relearn to write with beast-hands. In another, the easy familiar activity has been eternally jinxed by your inability to even start right, and you can't risk the rest of your materials, because that would shred your heart along with your nibs and splatter despair deeper into your soul than ink on the next twelve pages of the book.
And we know the Beast is of a turn of mind to recognize symbols and patterns, so the prosaic viewpoint is even less likely to recommend itself.
Awww nuu ;_; poor Beast... it's okay! Just practice with your different hand now and it'll work out! Don't... stab yourself with pens or something D: (which that last panel seems to forebode T_T)
Using previously written Beasts as a guide, I'd give about two-to-one odds for a destructive tantrum.
However, given that our dear MsMegan has shown herself happily willing to subvert the paradigm of prior Beasts (which by the way is awesome writing, MM), I'd say it's a fifty-fifty toss-up between smashing the pens and practicing with them until he relearns how to write and draw.
That third panel. I know that face. I have made it myself. That moment when you've just finished painstakingly sharpening your pencil lead to a sharp point to make an fine line and it snaps off. It's tragic.
Aaaaaaand there's the mood whiplash I was expecting. The Beast's hopeful mood was shut down when he broke the pen - indicating that he can no longer write or draw. I wonder if the pens in the drawer are also broken from previous attempts or if he's just going to keep trying. I hope it's the latter.