HUF Controller described deviation event when issuing a non standard altitude and then failing to point out traffic to an adjacent sector; claiming others duties caused momentary inattention.

Narrative

I had just arrived at work and taken the position; and was only mildly busy when the event occurred. A PA28 had just conducted a missed approach to Runway 17 and was turned by Tower to a heading of 240 degrees; climbing to 3;000 FT. I radar identified him and immediately issued him his IFR clearance to CMI. I told him to proceed on course (toward TTH) and to climb to 6;000 FT. The ceiling of our airspace over BMG is 5;000 FT; but just 1 mile southwest of the BMG the ceiling increases to 10;000 FT. Without realizing my error; I refocused my attention on other traffic in my airspace. After a couple of minutes I realized that Aircraft X was just inside the 10;000 FT ceiling area of my airspace and was level at 6;000 FT. I am unsure whether Aircraft X was clear of my BMG shelf area when he climbed out of 5;000 FT and it is possible that he might have briefly entered Indy Approach airspace for a mile; or two. Since Aircraft X would be running the boundary for several more miles I called Indy and initiated a pointout; which they approved. I work numerous aircraft in and out of BMG everyday and I 'never' issue an initial altitude higher than 5;000 FT; so I am not sure why I broke with my standard procedure. I experienced a moment of inattention at a time (just after sitting down) when I know that the risk of error is higher and it bit me. In the future I must take special care to prevent this type of lapse in attention.