Toilet full valve drips slightly when turning back on
I am with jack here a photo of the leak or a description would be helpful, 

at the shutoff valve not the fill valve on the “crapper” itself.
 A leaky shutoff valve the valve stem packing may need a slight tightening, the nut below the handle, give it a 1/4 turn clockwise and see if the drip stops, this is common with older valves. Sometimes the valves need repacking but many times just tighten the packing nut will seal things up and last for years.