Hmm! Hard to be sure as Viola hybridize. The spur is the clue. Viola reichenbachiana..Early dog violet The spurs behind the petals are darker than the petals......that are neither furrowed nor notched at their tips Viola reichenbachiana, The Early Dog Violet Whilst Viola riviniana ....common dog violet. It has a spur which is upturned and lighter than the petals, (the spur is often white or nearly so) and is notched or furrowed towards its tip. Viola riviniana spurs - Google Search: Common Dog-violet | NatureSpot Your pic is not quite clear enough for me to be sure but spur appears to be pale.
