Vial contamination? Will replace but looking for advice for the future

My dr already said I should replace vial. I’ve been cleaning the top well and inserting the 18g at an angle but last week the top got this V and now looks like it may be contaminated. This vial is supposed to last 3 months for me. How can I prevent this in the future. The rubber feels sort of brittle. I draw up meds for work but we mostly use single use vials but they’re much easier to insert an 18g into. Any advice? Thanks!