I take my photo with instagram that goes through to my instagram related blog on Tumblr (its different to the one I have here on WordPress). To then show what photos im posting on my Tumblr blog (so followers of my regular blog can check them out too!) I use the tumblr RSS feed.
I then pasted the tumblr rss link into the 'Flickr' widget as it allows you to put in an rss feed that ISNT just from flickr.
Theoretically you could use something like webstagram (or other instagram related feed sites) and post your rss in from there?
Thats how I do it anyway!
When I upload to instagram I just make sure the Tumblr button is checked and I know it goes through to both....
Helice11 - you can make a 'follow me on instagram' image and link through using that.
By using one of the 'text' widget boxes you can add some code in like this:
<a href="http://www.followgram.me/XXXXX">FOLLOW ME ON INSTAGRAM</a>
This will give readers a link to click on rather than an image.
Or to use an image, upload the image you want to use to your wordpress gallery so you have a url. Then put some code like this into a text widget:
<a href="http://www.followgram.me/XXXXX"><br />
<img src="XXXXXX.jpg" border="0"><br />
The XXXXX are where your links will go!
This doesn't take the user directly to instagram but to follow gram where other instagram users can follow from there.
Not perfect but some work arounds - hope that helps!