Hi TTB
The issue of a tattoo stretching is most noticiable on the stomach where (in my wildest dreams) you can lose a lot of weight or gain weight.
The chest area would only be notably affected if you went to an extreme of muscle or body building steroid chewing type of bulk.
If it is a fairly large tattoo there will be no effect to the naked eye on a normal bulk up.
Tattoos do fade and need a re-ink though every 10-15 years as they will blur with age but that is as the quality of your skin degrades – so stay out of the sun 😉
Enjoy and post up when done.
Matthew