Internet of Bio-Nano Things-based molecular communication system in nanonetworks is deemed critical for various applications in futuristic health care technologies. In this work, we envisage a new research direction and coin the term—“BioBlock”—a blockchain-inspired nanonetworking security mechanism since the existing macro-scale security solutions are not suitable for nanoscale. Specifically, we propose a biological ledger-based relay model to secure targeted drug delivery without affecting surrounding healthy tissues. In BioBlock, each successful transaction generates a block with genetic signatures of the bionodes in the nanonetwork, which eventually gets validated by the neighboring bionodes. We show the effectiveness of our model regarding energy utilization and information delivery while highlighting the average delay introduced in the network with an increasing level of security. We observe that the information delivery factor in the case of the naive approach is 90.59%, while in the case of a 6-fold secure approach, it is 89.77%. Eventually, we observe that the targeted drug delivery is not affected by the introduction of multifold security.