Onychomycosis in toddlers is an exceptionally rare condition, made even more unique by its association with behavioral habits like thumb-sucking. We present the case of a one-year-old male with persistent yellowish discoloration, onychodystrophy, and paronychia of both thumbnails. Dermoscopic findings, alongside culture results confirming Candida albicans, guided a successful treatment strategy using oral nystatin. This case underscores the critical role of behavioral factors in pediatric nail pathology and highlights the importance of integrating clinical, dermoscopic, and microbiological evidence for accurate diagnosis. This report elucidates an underrecognized pediatric presentation, contributing to a more comprehensive understanding of fungal nail infections and their management in early childhood.