The plant has been used by traditional medical practitioners in North-Eastern part of Nigeria to stimulate erection in male sexually. The plant is found on mountainous area growing in between rocks and contains menthol on the root bark.
Thanks sir Michael Uebel for the help, at least i have a direction but the problem is the plant am having is not a tree, rather a runner and its the root that is used not the step. The picture above is the whole plant speciemen
The above plant could be Plumbago zeylanica L. of Plumbaginaceae family (https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:687109-1). In several African countries the roots of this plant is used for the management of erectile dysfunction.