I accidentally sniffed leftover extra strength relaxer for hair. the chemicals burned my nose. i have a slight headache. should i be worried?

Get some fresh air: Hair relaxers have strong chemicals in them that can cause all sorts of problems to the scalp. Prolonged inhalation can be associated with upper respiratory issues, but a brief exposure, while irritating your nose is not likely dangerous. Step outside for some fresh air and take a big sigh of relief. You're going to be okay. Hope this helps.