Raised lines appeared in outline on 9 month old tattoo

[Bairn1876]

Hi guys, 

My 9 month old tattoo which I believe has always been fine, now seems to be raised in one area, outline only. 

 

I'm hoping it will go  back down but a bit worried this has happened. I've read a lot of different reasons why it could happen on other non tattoo forums from Google search but thought it would be best to ask guys with better knowledge. 

 

Thanks 

[Hogrider]

How long does it last? I have some of tattoos that will have raised lines for anywhere from a few minutes to a few hours. Some are eight or ten years old.