DOP Mii is the best way for people who don't know what they are doing to brick their systems (with using menu themes as a close runner-up).
If you have priiloader installed and you can access it by holding Reset on power up, you may be able to fix it.
If you have a NAND backup and have bootmii installed as boot2, you can fix it.
If the answer to either of these is no, then you've got yourself a new doorstop.
Had you come up us before you started messing with menus and DOP Mii, we would have told you that your mod is likely out of date or incomplete, thus the DSI problems. Remodding your system would have most likely gotten it working, and we would have given you a link to a guide to do that.