Would be much better for him to get another one or three and let them form a little bonded peer group, then run them alongside (other side of a wire fence to) the other sheep for a while before letting them join up. Probably safest to bring a few (two or three) of your last year's lambs in to the newbies' pen first, let them get to know each other, so they have already got some acquaintances in the incumbent flock when they all join up.
When you do introduce them, make sure there's lots of space, so they have a better chance of avoiding getting rammed. If they're smaller than any of the incumbents, you could make a creep area for them to go into for their own safety if needed, but you'd need to get them used to going in and out of it first, so they know it's there and how to get into it.