Sorry no-one replied sooner.
I think you might need to weigh the little one – althouth it’s probably a bit bigger by now – they grow very quickly at that age. I would take the scales outside to minimise any stress.
Then, as you’re feeding (hopefully cat, dog or meaty hog food) and offering water to the little one and the weather is still so mild, if the little one is over 350g and is behaving normally, turning up regularly, etc. I would be inclined to let it stay and keep an eye on it. As mentioned they do put on weight very quickly and it can be very stressful for them to be in captivity which would be the alternative. Some hoglets continue to visit all through winter – they don’t seem to mind the cold too much as long as they have somewhere sheltered to curl up.
If it weighs less than 350g, I would ring your local hog carer and take their advice. They will be familiar with your local weather conditions, etc.
Good luck. I hope all goes well.