At first I thought "jump the gun" might work here. However, I think a better choice would be to "get ahead of myself".

From wiktionary get ahead of oneself

• (idiomatic) To develop an opinion based on insufficient information or to take action prematurely.
• (idiomatic) To speak or write in a manner in which one makes points out of logical or chronological sequence.
• (idiomatic) To focus excessively on one's plans or on prospective future events without paying adequate attention to the present.

So one might say, "I may be getting ahead of myself here, but I wish to mention that .... "

At first I thought "jump the gun" might work here. However, I think a better choice would be to "get ahead of myself".

From wiktionary get ahead of oneself

• (idiomatic) To speak or write in a manner in which one makes points out of logical or chronological sequence.
• (idiomatic) To develop an opinion based on insufficient information or to take action prematurely.
• (idiomatic) To focus excessively on one's plans or on prospective future events without paying adequate attention to the present.

So one might say, "I may be getting ahead of myself here, but I wish to mention that .... "