It's used quite often to mean chest. It's a fill in for saying "breast", which is usually meaning "inside one's chest, near to their heart".

There's a quote attributed to Albert Einstein though I found no source to which is "Anger dwells only in the bosom of fools", which shows this application.

Shakespear also has Isabella say in Measure for Measure, act 2 scene 2 "Go to your bosom: knock there, and ask your heart what it doth know.", which seems most accurately to be describing the chest more vaguely.

I think that these two show how 'in [one's] bosom' often poetically means 'near [one's] heart", or 'close to [one's] chest'. The chest isn't the point of sentence, it's more a reference point for describing the actual subject location.