My first did this for a long time. One HV suggested a poor latch but the breastfeeding dept at the hospital said that some babies just do this. I went on to breastfeed her for 20 months, the first 6 months exclusively bf.
It can mean a tongue tie but not always and if your baby is otherwise fine and thriving is probably nothing to worry about. My 8 week old baby makes a clicking sound but her latch is fine and she's bright-eyed and bushy-tailed. Congratulations, btw!
Cheers she's my second dd and I fed dd 1 till 11.5 months so will Defo keep it up! She's putting on weight very well- may attend the bfeeding support group to check with a councillor about latch (I've been avoiding the group as I don't want to scare all the new mummies with my toddler!