Dry and irritated bumps could probably be the result of some kind of a skin infection on the outside of your vagina and, probably, not something that is within your body. However, to be absolutely certain, you should consult a doctor to be sure about this. There is also a very good chance that the bumps and irritating is because of using some kind of sanitary product like tampons, sanitary pads or panty liners. This could also extend to the use of some foreign substance like soap, a cream, some kind of medication you are taking, and so on. You would need to go back in time to when this problem did not afflict you and figure out what changed in your regimen after which the problem occurred.
Dry and irritated bumps indicate that the area is inflamed. Inflammation in the body occurs when there is some kind of a foreign body that has invaded or if there is an allergen in the area. Most allergies to the skin manifest themselves in the form of rashes like the hives or in the case of a chronic inflammation, peeling of skin. To be absolutely sure that there is no skin infection in the area, you should first apply some antiseptic to the area to combat a bacterial infection. If this has an effect then you should start using a cream that contains aloe vera and apply it to the area. Aloe vera forms a bandage-like coating on the skin preventing further inflammation. If the use of antiseptics does not work then you need to use a more powerful agent and that can be the use of tea tree oil. Tea tree oil has the ability to destroy nearly every microbe it comes into contact with and is one of the most effective topical applications. There is a danger in using this as well, which is that you would destroy the natural flora of the vagina.
The human vagina is not bacteria free. Just like most other parts of our body, there are bacteria that live here as well and for a very good reason as well. The predominant strain is lactobacillus acidophilus and these bacteria make the vagina slightly acidic and non-conducive for other strains and fungi to populate. By the use of tea tree oil, you could disturb this balance so as soon as you have finished with this, use a douche with some probiotic milk or use a tampon that is soaked in probiotic milk to restore the regular balance of flora in your vagina.