Stuff the pearl it sits on into the socket near the start of the tunnel.
And energy barriers don't only hurt you, btw.
Is that enough to help you out?

EDIT: Uh, before getting frustrated and giving up, post here earlier

EDIT2: Almost forgot this: Rule of thumb: If it flashes yellow, you are not doing damage. If it flashes red, you are.
That is, flashing yellow does often trigger something else that is needed for success. Like in case of this boss, you are not hurting it, but you are forcing it to go back further into the tunnel.
(Can be compared to poking someone with a stick (yellow) or a chainsaw (red)).