Your symptoms of the knee giving way while running suggest possible ligament weakness/instability, meniscus injury (damaged cartilage), or muscle imbalance around the knee, so it is important not to ignore them. For now, avoid running or high-impact activity, and follow RICE: rest, ice the knee for 15-20 minutes, use a supportive knee brace, and keep the leg slightly elevated if there is swelling. Start gentle strengthening exercises (especially for the quadriceps and hamstrings) and stretching once pain settles, preferably under a physiotherapist's guidance. Proper footwear and a gradual return to activity also help prevent recurrence. However, since your knee is giving way, it is best to consult an orthopaedic doctor for proper examination and, if needed, imaging like an MRI to confirm the cause and guide treatment.