EE was assisting spreading a telehandler forks, while they tilted mast down to facilitate tine adjustment, the right tine was moved, after EE began sliding the L tine outward. During this process, the R tine slid back unexpectedly. EE attempted to reposition the R tine w/EE's gloved L hand, EE L middle finger got pinched between tine and mast's lower bar. Skin tear on L finger.