I am sorry to hear that poor Lady had a swollen nose top on Monday and now has black bleeding bumps on her nose.
Thank you for the picture.
It sounds like she suffered an allergic reaction to something, and all of the inflammation allowed a secondary infection to occur.
If the infection is superficial and she isn't licking too much then you may be able to treat this at home successfully.
You can continue antihistamine (piriton) use if it seems to help.
It may help to shave her nose in that area to allow air circulation. Trapped moisture tends to worsen things.
You can try a shampoo called Oxydex to clean the area well twice daily. See this link for an example (http://www.entirelypets.com/oxydexshampoo.html )
Don't allow her to lick it as it does contain peroxide which could irritate her stomach and lead to vomiting.
Another option is a human acne product called phisohex. You can clean the affected area twice daily, again being careful to let it sit for a few minutes to allow it to flush out the follicles and not allowing her to lick as it also will upset her stomach.
I would clean the area after eating.
If this isn't clearing it may be deep enough that she needs oral antibiotics. Or it may be complicated by a demodex mite infestation. These mites aren't contagious and are present in all dogs but in some dogs their immune system is such that they are allowed to proliferate in high numbers. They are more commonly a problem in young dogs. Her veterinarian can scrape the area or biopsy a lesion to look for them and get her on oral antibiotics if the topical treatments I mentioned don't work.
Please let me know if you have any further questions.