854. Trimming One's Mustache and Fingernails
122:4 If one's mustache interferes with eating, it seems that it should be permitted to trim until the week of Tisha b'Av but not in the week of Tisha b'Av. (Others say there is no reason to be stringent in this matter even during the week of Tisha b'Av - Shaar HaTziyon 551:90.)
122:5 Cutting one's fingernails is only prohibited during the week of Tisha b'Av. A woman who needs to trim her nails in order to go to the mikvah may do so even then. A mohel may also trim his fingernails in order to be able to uncover the membrane.