Needle insertion into soft biological tissue is a common medical procedure used in vaccinations, biopsies, and brachytherapy. While single-needle insertion has been extensively studied , the mechanical interactions associated with multiple needle insertions have received limited attention, despite its importance in treatments such brachytherapy for prostate cancer treatment. The aim of this work is to develop a finite element (FE) framework capable of simulating the mechanical response of the human prostate to the sequential insertion of more than 20 needles, reflecting a realistic High-Dose-Rate (HDR) brachytherapy procedure. The proposed framework models the penetration of cylindrical needles into soft biological tissue using a node decoupling algorithm that enables progressive insertion into the tissue and incorporates a patient-specific geometry of the prostate gland. The numerical results are validated against simulations performed using the commercial software ANSYS LS-DYNA to assess the accuracy and robustness of the proposed solver. Furthermore, simulation outcomes are compared with actual clinical cases provided by collaborating clinicians. The proposed framework has the potential to enhance pre-operative and intra-operative planning in prostate brachytherapy by accounting for prostate deformation and movement resulting from the progressive insertion of multiple needles. This enables clinicians to optimise treatment delivery while avoiding critical anatomical structures, such as the urethra.