The closest beach to Saint Nicholas (Sithonia) is Tower Beach, just 2.2 km away. Within 15 km there are 29 beaches; below are the 12 closest to Saint Nicholas, ordered by distance. Photos, map, reviews.
2.2 km from Saint Nicholas

2.4 km from Saint Nicholas

2.6 km from Saint Nicholas

3.4 km from Saint Nicholas

3.6 km from Saint Nicholas

4.0 km from Saint Nicholas

4.7 km from Saint Nicholas

5.0 km from Saint Nicholas

5.0 km from Saint Nicholas

5.6 km from Saint Nicholas

5.9 km from Saint Nicholas

6.2 km from Saint Nicholas

Tower Beach, just 2.2 km from Saint Nicholas. The rest are listed below, ordered by distance.
Within 15 km of Saint Nicholas there are 29 beaches, with 69 across Sithonia in total.
Based on user reviews: Tower Beach (★3.8), Schoinia Beach (★3.8), Trani Ammouda (★3.8).
The beaches are spread out around Saint Nicholas. A car makes exploring much easier — local buses and taxis are limited outside peak season.
Saint Nicholas is on the Sithonia side of Halkidiki, in northern Greece. The nearest airport is Thessaloniki (SKG); from there a car is the most convenient way to reach the Sithonia villages.