The epoxy should feel well-cured after 24 hours, however, full cure and maximum hardness can take up to 7 days, depending on temperature. If it is still tacky, this likely means it was due to incomplete or inaccurate mixing. Small areas can be improved with an alcohol wash, but larger areas will need to be removed. If it is soft enough, try scraping it off. Otherwise, you will need to sand it down and pour it again.