Hairy leukoplakia is usually associated with HIV infection. However, it might be difficult for a person that is not health care professional to differentiate hairy leukoplakia from other forms that are usually caused by some less serious conditions. While every other leukoplakia is considered premalignant, it is not the case with oral hairy leukoplakia. Leukoplakia itself can be developed in several days, but in that case it is more probable that the leukoplakia is caused by infection and not by immune disorder. Immune deficiency usually takes longer to appear then the 8-10 months after HIV exposure that you reported.
You might want to visit a doctor to examine if the leukoplakia is really a hairy leukoplakia. Meanwhile, you might want to avoid some of the predisposing factors: smoking, alcohol.