Yes, I would try to weigh the little hog. Have a box ready in case it needs to go to a hog rehabilitator.
The minimum weight needed to survive hibernation is 450g. But if the hoglet is visiting for food every night it might be ok to let it stay and keep feeding it if it weighs a bit less than that. They do put on weight very quickly at that age.
There is no guarantee that a hog will survive hibernation even if it weighs more than 450g. Likewise there is no guarantee that a hog being overwintered by a carer/rehabilitator will survive. It is very stressful for hogs to be taken into captivity and not all will survive. Hence that I would let it stay in its natural environment even if it currently weighs a bit less than 450g, as long as you are providing good quality food as well as water and it is visiting every night.
Things might be a bit different if, for instance you are in the north of the country where the weather may be colder. You can always contact a local carer/rehabilitator (who will know the weather conditions in your area better) and take their advice. You can get contact details of your local carers/rehabilitators by ringing BHPS 01584 890801.
Good luck – I hope all goes well.