It is a strong way to express a lack of concern or complete indifference toward a situation, opinion, or person.
The phrase is considered vulgar and is generally reserved for informal settings or used in a confrontational, "mean" way.
On video platforms, the tag combined with this phrase often identifies content with the following themes: What does aha wiem i mam to w dupie;) mean? - HiNative
A slightly less vulgar but still slang version is "mam wyjebane" (I'm totally indifferent). A polite alternative is "nie obchodzi mnie to" (it doesn't interest me). Context in Social Media (#shorts)