Sorry Bally,
Its entirely possible for an increase in thrust to cause a pitch down, it just depends where the line of action of the force is relative to the C of G.
If its above, increasing thrust causes a pitch down. If it below, causes pitch up.
Its just basic mechanics.
What happens next, for most aircraft most of the time, is that speed increases causing you to either start to climb or to have to trim nose down to avoid a climb. There may or may not be other factors mixed in (e.g. changes in prop effects, changes in downwash on the tail etc).
Don't confuse the effect of changing power with changing airspeed, nowithstanding that changing the former will also tend to change the latter.
CPB