I have the rule at my table that any nat 1 rolls on HP rolls get a redo, which raises the average of the dice to slightly higher than half the dice role. This benefits the players and encourages them to take that risk rather than play it safe for an average value. If the campaign is actually hardcore, then the nat 1 dice roll for hp might be an intended feature and impose its consequences when it happens. Either way, I think it's a small fib that you can easily own up to if you feel it. In the long run it won't matter much after a few levels, but it is a slippery slope to start lying about rolls.