This is a good sign. It means he can tell people he knows from people he doesn't. Hold your baby when he meets people. Let him get used to them slowly, especially child care providers. Or you could have the new person hand him a favorite toy.
Babies love babies.
When you are around town, you will meet other parents with their babies. Babies really like other babies. Make a date to meet another parent and baby at the park or at your home. Make it a fun time. See what the babies will do with each other.