A little discharge coming from thorn puncture wound?

Be seen. It sounds like you have an infection. Be seen. There are many infections that can be from puncture wounds, and thorn wounds in particular.
Sporotrichosis. There is a fungus infection that can be transmitted from plants, usually rose thorns. It is causes by sporothrix schenkii, and can create serious problems. This should be seen by a doctor, cultured and perhaps even biopsied. See an infectious diseases specialist.
Get it looked at. Puncture wounds can lead of severe infections especially in diabetics. With puncture wounds, one may also develop tetanus. In case of infection, do not delay treatment as you may need antibiotics. Have the wound properly evaluated and treated to avoid preventable complications.