Adding butter to milk does not make it creamy. Your ice cream probably got a good enough consistency from the milk alone. That's not unusual, most commercial ice cream producers don't use cream either.
If you are asking what to do for the next batch: don't mix butter and milk, this is not just pointless, it leads to the fat globules you noticed. You can use cream for a richer ice cream, or milk if the creamless one is sufficient for you.
If you are asking what to do with this batch: The chances are not good. You can try melting it in the fridge, straining the ice cream base and churning it again. But the quality will be worse when churned for a second time, so I'm not sure it's worth the effort.