Boar face is the Lanchhana (emblem) of Vimalanath, the 13th Tirthankara. In Jain iconography each Tirthankara has a fixed symbol to help devotees identify him, and Vimalanath’s symbol is the boar. The emblem reminds us of his qualities and life-story, just as other Tirthankaras have their own signs (e.g., Adinath with the bull, Mahavira with the lion, etc.). There are small differences in the exact symbol between Digambara and Śvetāmbara traditions for some Tirthankaras, but the purpose and core meaning of the emblem remain the same: it is a spiritual sign to identify the Tirthankara and inspire his teachings. You can read more about the boar emblem for Vimalanath and the 24 Tirthankaras here