Actual Infinity in Reality?

[Anomalocaris]

Is a singularity very dense matter? Yes.

Infinite? I don't think so.

I heard a physicist say that when they get to having to put infinities in they know theres something wrong with the maths somewhere.

Not exactly so.

Physicist are also susceptible to brash talk. The difference is behind the brash outward talk, the ethos of the entire physics community is the willingness to do the ground work and take the time to verify or refute the talk using a consistent framework. It could well be that in 50 years, physicists of the future look back at the present and laugh at gutlessness or false confidence of the current generation of physicist in their refusal to continence infinity as a proper solution.

When physicists say they know, in here they mean they strongly suspect there is something wrong because infinity correlates to no clearly known analogue in realty, and can not as yet form any the basis for further predictive mathematical manipulation.

They strongly suspect the solution to the practical problem of what to do with the seeming mathematical dead end much more likely lies with discovering any errors or insufficiently accurate approximations in the road map leading to the mathematical dead end,  then in finding a further path from that seeming dead end onwards.