Unplug it immediately and Stop using it until the problem is properly diagnosed and rectified by an expert.
You risk death to you and anybody else in the property - the mains-tester shows the presence of Voltage - the neon strikes at typically 90V.
The "tingle" you felt will have been FULL MAINS VOLTAGE - you did not die because you were not properly earthed.
Lord Finchley tried to mend the Electric Light
Himself. It struck him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisan.
Peccavi, January 2013