Sometimes it’s ok to let yourself obsess. Sometimes it isn’t.
Ask yourself this: Why am I obsessing?
If it’s because of anxiety, then try to fight it, if you can. Try to side-step it. Try to come back to it later.
If it’s because you’re fascinated or interested, then don’t fight it. Let yourself explore and learn. Listen to your brain. It’s telling you you’ve hit upon an interesting nugget of truth.
For what it’s worth, obsession isn’t always bad. But to be fair, when it’s bad, it can be really bad.