Don't take any more until the nausea goes away or it's been 12-24hrs, whichever happens fist. And next time, regardless of when you dose, try to just take half what made you nauseous today.
In terms of nausea, OTC stuff that really helps is ginger (especially strong ginger tea). Seltzer water helps some. But the biggest thing besides ginger is simply laying down in cool dark room to relax. Ideally on your back.
You can also try diphenhydramine or motion sickness OTC stuff. I actually found DPH worked well to deal with minor nausea, but others need something more powerful. In terms of prescription meds, ondansetron (Zofran) works really well at preventing nausea.
Some people also find cannabis helpful, although now I'm more an advocate for CBD use as opposed to just normal high potency THC buds/concentrates. I find CBD way more effective for nausea, sleep, etc than I do THC.
I have a feeling you may have just taken a little more buprenorphine than you needed. The side effects from taking more than necessary aren't fun and tend to involve a lot of nausea. It will wear off, though it may take a day.
The stuff has a very long half life and is very potent, so try and be careful in terms of figuring out just how much you need. Buprenorphine is one of those meds where less is often more in terms of desirable results.