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Thanks for putting up your question on Just Answer.
At 14 years of age, it is extremely unlikely that you still have a milk tooth in the lower anterior area. Sometimes, pressing a tooth with the tongue can give an illusion of tooth mobility, and that is what im suspecting is happening in your case.
However, to be sure that there is no over-retained milk tooth remaining there, please see a dentist. A simple physical and maybe a X ray will clear this up.
Nothing serious, nothing urgent and nothing to get worried about.
Hope this answers your question. Feel free to contact me again for more information. Please leave a positive rating for me if this answer has helped you. I do not get credit for it otherwise.
Good Luck !