You really ought to halter your new foal straight away.
We take our new born foals out into a small well fenced paddock on the 2nd day of their life, and they start to get used to their halter gently, with a hand on his rump to carefully guide him forward, it will take a bit of care and persuasion and you need someone to lead mum too.
Just lead the foal steadily behind the mare and turn them out for about an hour, then lead them in.
The period you leave them out (weather permitting, don’t put them out in the cold and wet) can be increased little by little.
