Dear Shoeb Mohammed,
Really nice to hear that you have good exp. in SD testing, Hope you have good knowledge in SD business process also, and now you are exploring the functionality of SD.This gives you more flexibility in SAP Sd module.
Also learning ABAP is an additional benifit being a java developer you can make it in short time.Also you can try exploring on mobility applications as now a days many functions are moving to mobile.
Try to look at (SD) integrations part with other modules as well,Once you are expertize in one SAP module you can easily look at other related modules and its process which will be helpful to you during your module integrations.
Wish you all the best, happy learning !!
Regards,
Rao