In MA and NH you can’t have a vehicle inspection without a valid registration. You may not have a choice waiting to register. You may want to consider looking for an inspection place outside of your location, maybe less wait time? I am not sure about the comment above regarding not getting a ticket, I know cops that would give their own mother a ticket. Also, in NH you won’t get a Rejection sticker like in MA. Having just been thru this, NH allows 10 days post expiration to have any issues resolved. I went over the 10 days, thankfully didn’t get pulled over. Auto dealerships in my area perform inspections, maybe that’s an option. Good luck!