There may have been an injury to the peripheral nerve axons originally. In this type of injury, the nerves may have been damaged permanently, although some nerve regrowth can occur over 12-18 months after the injury. The hands and feet nerves, being farther from teh central nervous system, are more vulnerable to injury, and take the longest to recover.
Once damaged, the pain may have settled down, but the damaged nerves may be more vulnerable to any further injury (less 'reserve')
In any case, the cause of the second worsening may be something else, and should be worked up by your doctor to ruleout other conditions, such as diabetes, sjogrens syndrome, monoclonal gammopathy, HIV etc
Most of these tests are simple blood tests. Electrodiagnositc studies are unlikely to be of much benefit. Sensory neuropathies can now be investigated by a new test - epidermal nerve fiber analysis from a skin biopsy, available at some of the larger neuromuscular centers (such as the Cleveland Clinic)
Chronic lyme disease is an unlikely diagnosis.
Good luck