I've created a tag through Bitbucket website --> placed it by mistake on a commit in Develop branch not the master

I wish to delete the tag. Connecting to my repository through SourceTree with Develop branch checkout. The tag isn't showing when clicking 'tag' on the left panel nor when clicking in 'tag' button in the menu and the tag modal window opens with no tags to remove
Please advise (I haven't installed git on my computer to access through command line)
