I did something similar two weekends ago trying to get new bindings dialed in. I was cranking them down way too hard and didn't have them lined up correctly so the buckle pressed right into the toe. At the end of the day I would've sworn I was going to have bruising but luckily I didn't. Sounds like a strap issue rather than boot issue, or I should say it sounds like my strap problem. I have the synapse in wide and there's no difference between the 10 & 10.5, the 10 has a thicker footbed is all.
159w Lib Tech Attack Banana, MC Metafuse, Salomon Synapse Wide