Adopting second dog?

Hi, I need help, we have a bearded collie cross and this morning took him to meet a little west highland terrier, hoping to give Buddy a play mate. The westie is ex stud but came running out keen to meet. Our dog, buddy, was not as keen, and became very barky and jumping up whenever the little one approached...Is this normal, will they ever be friends. I really want to make both dogs happy. please help me decide.

Buddy is 5 and has been an only dog, since we brought him home at 8 weeks old......