What is and how do I go about fixing this mystery bubble

Not sure if it was there when I first got the bike but I don't think it was, noticed it a few weeks after I got it.

It's soft and squishy like there's some liquid (gas?) inside and it's growing slowly as it used to be above the Honda sticker and now it's bulging under it too

Any answers as to what it is and how to fix it are appreciated

I'll be repainting the whole bike at some point so a "dirty" fix that ruins the paint but leaves it safe from further damage (rain or the bubble coming back) is fine

What does the inside of the tank look like? Rusty? That looks suspiciously like a pin hole leak under the paint

That's a pin hole in the tank alright, best to pop it before it gets bigger and lifts more paint

For a temporary fix I've used this from Permatex

https://www.permatex.com/products/adhesives-and-sealants/specialty-adhesives-removers/permatex-fuel-tank-epoxy-putty-1-oz/

4 hours ago, Presson

What does the inside of the tank look like? Rusty? That looks suspiciously like a pin hole leak under the paint

I'll send a picture when I'm off work or tomorrow in the sunlight, from what I saw when filling up the inside looks great (are these double walled and maybe the outside is cooked?

3 hours ago, Thumbs

That's a pin hole in the tank alright, best to pop it before it gets bigger and lifts more paint

For a temporary fix I've used this from Permatex

https://www.permatex.com/products/adhesives-and-sealants/specialty-adhesives-removers/permatex-fuel-tank-epoxy-putty-1-oz/

Noted, I'll look into finding an equivalent available here (Ireland)

You mention temporary fix, what's wrong with leaving this for good? What's the alternative for a permanent fix?

52 minutes ago, Divilus

I'll look into finding an equivalent available here

This looks like it could do the job although there's no mention of fuel resistance 

https://amzn.eu/d/0ijJMGsB

3 hours ago, Divilus

This looks like it could do the job 

Found the exact same one instead, 10 quid and 5 delivery

https://www.tradeinn.com/waveinn/en

The place I got it if anyone happens to look for it later