introducing new dog

Well, I think i rushed it. Our new very small dog is about 9 months old and has been home for 3 days, and is so nervous and submissive that I thought it would be OK to let Tigger approach her. Tig has been nothing but curious, not afraid at all. He bounded over to the pup in his usual "fools rush in" manner, and the pup freaked out, growled and snarled. I guess I will have to wait it out and continue to keep them separate and just let them sniff each other under the door for a while longer. I also made the mistake of not controlling/holding them -- Tigger approached much faster than I expected. Any other tips?