They can take some time to get going if they got chilled to start. Keep feeding him colostrum frequently tonight, it's important they get fed little and often to keep warm. Make sure he doesn't get cold again, heat lamp or hot water bottles may be needed, or even in the house for first night if very cold.
Afterbirth can take some hours to pass but if not gone by 12-48 hrs or the ewe is unwell at any time, ask your vet for advice.