First, DNA/RNA can actually enter the nucleus. Nuclear import is controlled by special amino acid sequences known as nuclear localization sequences. This, along with importin (transport protein) allows macromolecules to enter the nucleus through the nuclear pore complexes. tRNA, for example, are imported back into the nucleus, which has been shown in yeast. Plasmid DNA import has also been demonstrated.

When a cell divides, it’s nuclear envelope breaks down, so the mitotic spindle apparatus can invade and attach to the chromosomes. Then, the viral nucleic acids can interact with the hosts’. HIV, howeve, can enter the nucleus even if the cell isn’t dividing. It’s thought that the HIV genome uses the host’s cellular machinery to move into the nucleus. The HIV cDNA (result of reverse transcription) is coated with a myriad of proteins which allow it to cross into the nucleus.

Figure 1 in this paper should give you a good visualization: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3325773/

TL;DR: HIV sneaky. :( The idea of the central dogma of biology has some loopholes, with reverse transcription, and direct translation from DNA to protein. Always* exceptions to rules, that’s what makes science so amazing.