What filesystem format is being used on the SD card?  Connect it to system then run 
sudo blkid command in terminal to find out if you don't know.  For example here is my output with a USB stick connected (don't have an SD card) and it's shown using 
TYPE="vfat" at /dev/sdc1.
Code:
bill@Gold:~$ sudo blkid
[sudo] password for bill: 
/dev/sda1: LABEL="Mint16Xfce" UUID="16268cf7-b146-4ae5-b8a8-c02125bd87d9" TYPE="ext4" 
/dev/sda3: LABEL="DATA" UUID="ceee2524-7df2-4d21-a1f7-9e7e55c722cc" TYPE="ext4" 
/dev/sda5: LABEL="LinuxLite2" UUID="a9222190-0805-47ef-a2e2-e98b19d84b54" TYPE="ext4" 
/dev/sdb1: UUID="c4933327-f314-42ee-8b4a-ec3e48a0ded5" TYPE="swap" 
/dev/sdb2: LABEL="DataBackup" UUID="50e44bdd-edba-4b99-89a4-8fea89c18c1d" TYPE="ext4" 
/dev/sdb5: LABEL="ISOs" UUID="15443ba5-bdd0-4f0d-ae19-420022a7aab7" TYPE="ext4" 
/dev/sdb6: LABEL="HomeBackups" UUID="aac3b231-c9e8-4960-9f9d-bff3a1856e0e" TYPE="ext4" 
/dev/sdb7: LABEL="VBoxHDs" UUID="3e68db3c-2acd-4718-812e-93e10bf63cf5" TYPE="ext4" 
/dev/sdc1: LABEL="KINGSTON" UUID="8A44-F1CF" TYPE="vfat"
If it's using either Ext4, 3, or 2 format, then maybe the mount point for the card is owned by root and all you need to do is change it to your username.  Mount the card in whatever way you normally do, then run 
lsblk command in terminal to see what the mount point is.  Continuing with my example, here you can see my USB got mounted to /media/bill.
Code:
bill@Gold:~$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 298.1G  0 disk 
├─sda1   8:1    0    25G  0 part 
├─sda2   8:2    0     1K  0 part 
├─sda3   8:3    0 223.1G  0 part /mnt/DATA
└─sda5   8:5    0    25G  0 part /
sdb      8:16   0 596.2G  0 disk 
├─sdb1   8:17   0     9G  0 part [SWAP]
├─sdb2   8:18   0   230G  0 part 
├─sdb3   8:19   0     1K  0 part 
├─sdb5   8:21   0    40G  0 part /mnt/ISOs
├─sdb6   8:22   0    40G  0 part 
└─sdb7   8:23   0   200G  0 part /mnt/VBoxHDs
sdc      8:32   1  29.1G  0 disk 
└─sdc1   8:33   1  29.1G  0 part /media/bill/KINGSTON
sr0     11:0    1  1024M  0 rom 
Now run command to list (in long form) files mounted under that mount point ("/media/bill" in my case). Use 
ls -l followed by a space, then the mount point.
Code:
bill@Gold:~$ ls -l /media/bill
total 16
drwx------ 9 bill bill 16384 Dec 31  1969 KINGSTON
Mine says it's owned by me:  "bill     bill".  If yours says "root     root", then change ownership of the mount point to yourself.  (The "-R" in the command recursively changes ownership of all the files under the mount point to you as well.  If you don't want that to be the case, then don't include the "-R".)  Substitute your username in place of "bill" and your mount point in place of "/media/bill" in terminal command below:
Code:
sudo chown -R bill: /media/bill