Momentarily shorting the battery + to ground shouldn't hurt anything,
I've managed to to this a few times myself.  Does everything else work?
If not, you may have damaged the internal connections inside the
battery.

If lights, etc., work, it could be something purely coincidental.  Check
the large wire from the battery to the starter for any breaks or loose
connections.  Also check the smaller wire from the starter to the
ignition switch.  Try to turn the starter by shorting out between the
small terminal and the large post with a screwdriver.

There must be something loose or broken somewhere in the starter
circuit, or the notorious failure of the ignition switch could have
happened while you were working on the battery!

--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Driven since 1969)
'74 MGB GT (Restoring)

Assisting on Restoration:
'72 MGB GT (Daughter's)
'64 MGB (Son's)

Parts cars:
'68 & '73 MGB, '67 MGB GT