Employee was replacing bolts and wrench slipped off causing employee's left thumb to contact the hammer base. DOI was 09/03/20, did not seek treatment on DOI. Emp was scheduled for vacation on 09/04 thru 09/13. Upon empl return of 09/14/20 from vacation, emp informed the employer that treatment was sought on 09/12/20 and the care facility confirmed a fractured left thumb.