Welcome to the board.
And about the unusual growth. I had one do the same and posted about it here
Have you seen a flower spike like this before
I think it’s fairly unusual as I’ve been growing Oncidiums for a lot of years and I’ve only seen it this one time. Much more common is the situation where a sort of mini-pseudobulb grows out of the apex of a much larger pseudobulb. Species Oncidiums are not very common in cultivation so the members of the alliance we come across are mostly complex hybrids and their genetics is basically pea-soup so anything is possible.
Is the plant you are showing there the same hybrid as mine ?
---------- Post added at 07:39 AM ---------- Previous post was at 07:26 AM ----------
Sorry, just noticed you also asked how to care for it. I’ve just been out to our shadehouse to see what happened to it and the plant is there but the weird growth is not. I don’t remember if I cut it off or just ignored it and that section died off naturally. The plant has thrived.