In auto body there is an old trick of taking a diffused flame and moving round and round the small dent until you heat all the way to the middle then tapping it from the outside with a hammer round and round and it pops out - this is used on door dings I don't think it will work on round tubes I have never tried I just fill them with filler.
Someone mentioned the old drill a hole and pull out run for the hills if a body shop does that anymore that was 20 years ago. Today we have two tools one uses an electrical current through a handle that you hold one wire gets grounded to the metal the other has a trigger that you hold you put the tip in the dent pull the trigger and it welds itself to the metal then you hold the trigger and pull out the dent then release the trigger and it releases from the metal really cool but a cheap one is over $700
The other welds a small rod onto the metal - one brand is Uni Potter the other is Spitzinegal or something like that you then use a slide hammer tool to pull the dent then you can just snap off the rod. I would not recommend this for bike tubing it will just pull a hole through.
I have worked in metal all my life I would say leave it alone and not be so picky or fill it and repaint If it is something worth lots of money pay to have the tube replaced
Sam DiBartolomeo
Riverside CA