Stuck in landscape mode and will not lock

Just earlier today I dropped my phone, it wasn't a great distance really, but onto tile flooring. Now when the phone is on it says in the landscape view even when the keyboard is closed. If I move the keyboard the slightest bit out it goes back to portrait and I can usually get it to stay there so long as I don't budge the keyboard at all. However that's not exactly always practical and if I budge the keybord at all it becoms unlocked and goes to landscape again, and the phone doesn't lock at all until I get it back to portrait.

I'm guessing this is a mechanical problem with the slider from the fall then, but could I take it to be repaired at all? Or is it even something I might be able to fix on my own? Much thanks.