The tinniness is something your brain adjusts to and prices in, and if your hearing aid is properly set up, it is very likely that to start with it will sound tinny if your hearing is deficient with high frequencies. It is boosting those frequencies to make up for your lack in hearing. You probably need a good 2-6 months to adjust.

Mine were exactly like this to start with and over time the effect goes away such that you don't notice. I'd recommend if you do actually have hearing problems, sticking with it for quality of life improvements.

Me, too.